An oil cooler for cooling transmission oil maintains a temperature of the transmission oil at a predetermined temperature to prevent from excessively increasing due to slip of transmission friction components. Further, the oil cooler maintains fuel consumption even when friction loss increases as oil viscosity increases by excessive cooling of the transmission oil. Such a conventional oil cooler can be classified into an air cooled oil cooler and a water cooled oil cooler.
The air cooled oil cooler includes an oil cooler installed at a front side of a radiator through which outside air smoothly flows. A bypass valve is installed in a pipe connected to a transmission and opens/closes depending on a temperature of a transmission oil.
The bypass valve maintains the transmission oil at a predetermined temperature, such that when the temperature of the transmission oil is higher than the predetermined temperature, the transmission oil flows through the oil cooler via the bypass valve. When the temperature of the transmission oil is lower than the predetermined temperature, the transmission oil cannot pass through the oil cooler, thereby flowing back into the transmission.
However, since the conventional oil cooler has the bypass valve that is connected to the transmission to open/close depending on the temperature of the transmission oil as described above, and is installed in a pipe that connects the transmission and the oil cooler, a piping layout is complicated due to a relatively large bypass valve in the pipe, thus degrading spatial utility of an engine compartment.
Further, with the bypass valve applied to the conventional oil cooler as described above, since each of constituent elements needs to be sequentially fitted and assembled to a valve mounting hole of a valve housing, it is difficult to precisely install each of the constituent elements, excessive assembling time is required, and manufacturing cost increases.
In addition, when the transmission oil does not need to be cooled, since some of the low-temperature transmission oil cooled in the oil cooler flows into the bypass valve from a transmission and then flows back into the transmission, rapid warming of the transmission oil is difficult due to a high-temperature bypassed transmission oil.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.